1. Field of the Invention
This invention relates to a method and apparatus for reproducing signals recorded in a plurality of slant tracks on a recording medium and, more particularly, relates to a method and apparatus for reproducing signals containing a digital information signal and a pilot signal using a rotary head and employing the pilot signal to control a tracking alignment of the rotary head.
2. Description of the Prior Art
When a video signal and an audio signal are recorded on a magnetic tape by a helical-scan rotary head to form one slant track by one slant track thereon at every unit time and then they are reproduced, it is known that the video signal and audio signal are recorded and reproduced in pulse-code modulated (PCM) form. The reason for this is that if the signals are pulse-code modulated, the recording and reproducing thereof can be made with high quality.
In this case, tracking control for controlling the rotary head to accurately trace the recorded tracks upon playback is typically carried out such that a control signal that has been recorded along one side edge of the magnetic tape in its width direction by a fixed head is reproduced by the fixed head and the reproduced control signal and the rotary phase of the rotary head are made constant in phase relation.
This known control method requires the use of a special fixed magnetic head for the tracking control. The provision of such fixed magnetic head has a disadvantage that when the recording and reproducing apparatus is desired to be compact in size, its mounting space proposes a problem.
One approach to overcoming the disadvantage by use of the fixed head is a proposed tracking control method that does not use such fixed magnetic head but uses only the reproduced output signal from the rotary magnetic head to carry out the tracking control for the rotary head. This tracking control method is disclosed in, for example, U.S. patent application Ser. Nos. 560,958 filed on Dec. 13, 1983, 584,313 filed on Feb. 28, 1984 and 693,270 filed on Jan. 22, 1985 and assigned to the assignee hereof.
This tracking control method relies upon the fact that it is easy to time-compress and time-expand the PCM signal and hence it is not necessary to record and reproduce the PCM signal continuously in time, unlike an analog signal. Hence, the PCM signal and another different signal can easily be recorded on separate regions of each of the plurality of slanted tracks.
When the PCM signal is time-compressed and magnetically recorded on a recording medium by a plurality of rotary heads to form slanted tracks with no guard bands between adjacent tracks, a plurality of tracking control pilot signals are recorded in the longitudinal direction in each track to form a record region independent from the record region for the PCM signal. Upon playback, the recorded track is traced by the rotary head having a tracing width greater than the track width, and the tracking of the rotary head is controlled by the pilot signals reproduced from the tracks adjacent the track being traced by the rotary head.
Such tracking control method is required to be stabilized regardless of the characteristic of the magnetic tape used as a recording medium and the sensitivity of the rotary head.